
Some bitches do spread it around when they are in season!! It's a calling card. It could also be she's feeling some 'discomfort' from her enlarged vulva which could be sending her mis-messages that she needs to pee.
If you are unduly worried, collect some of her urine and ask your vet to run a urinalysis. To be sure she's not picked up an infection. She's 'wide open' when in season after all and only needs to squat in the wrong place. Which is why, or part of it, I didn't take my bitches off our property when in season.
Spay - in another couple of months?